View full size(Courtesy skytruth.org)MODIS/Terra satellite image taken May 24, 2010, possibly shows oil slick and/or sheen deeply entrained in the Loop Current and transported far to the south of the leaking well (dashed orange line). Scientists believe favorable winds and a high-than-normal discharge of freshwater from swelled rivers may be keeping the spill off the Alabama coast.Scientists believe that a higher-than-normal amount of freshwater flowing out of Mobile Bay has played a key role in keeping the Deepwater Horizon oil slick from washing ashore in Alabama so far.

Favorable winds have helped as well, scientists said.

The Alabama and Tombigbee rivers flow together above Mobile Bay to form the Mobile/Tensaw Delta, which, after the Mississippi River, amounts to the second-largest river system draining into the Gulf of Mexico.

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Heavy rains in Alabama, Tennessee and Georgia in late April and early May meant Alabama's rivers have been carrying up to 10 times more water than is typical at this time of year, according to river gauge data on both the Alabama and the Tombigbee.

"The 30-year average is about 20,000 cubic feet per second," said Kyeong Park, a University of South Alabama and Dauphin Island Sea Lab scientist who specializes in how water moves through coastal systems.

"In the first third of May, we had almost 200,000 cubic feet per second. That's a really high freshwater discharge, especially this time of year."

Park noted that from April 22 to 25, the oil plume from the Deepwater Horizon well site was expanding to the north by the day and appeared to be making a beeline for Mobile Bay. Then, beginning April 26, it stopped moving north and began stretching toward the east and west. By the 29th, the plume had moved well away from Alabama.

The movement of the oil slick, Park said, correlates with the spike in flow seen in the Alabama rivers, which resulted from a huge storm system that caused unprecedented flooding in Tennessee.

"But the entire signal cannot be explained by the rivers," Park said. "The other side of the coin is the wind. We have had very little south wind, which would be bad for Alabama. We've had some southeast winds, but we had the high river flows those days. The conditions have been very favorable for us."

Park said his modeling and data apply only to oil moving on the surface. The influence of wind and freshwater flow, the two parameters he is considering, diminish dramatically below the surface, he said.

"Dispersed oil and tarballs, things below the surface, I cannot tell you what is happening with them," Park said.

George Crozier, director of the Dauphin Island Sea Lab, said Park's work provides the best explanation he's heard of how Alabama beaches and marshes have avoided the oil landfall that has struck Louisiana.

"This is all circumstantial evidence, but it is the best I've seen. It is the most plausible explanation I've seen," Park said. "From this point on, it goes to how quickly BP can seal the leaks. As long as it keeps leaking, there is the chance we will see oil in Alabama. If we do not have high rainfall in the upper part of the state, then we are going to go back to 20,000 cubic feet per second. We might not be as lucky as we have been."

View full size(AP Photo/Jay Reeves)A tugboat pulls orange booms in Mobile Bay near Mobile, Ala., Monday, May 10, 2010. Crozier said Park's work raises the question of whether it might be possible to manipulate the flow coming out of the Mobile/Tensaw Delta by allowing more water to escape from numerous dams along the Alabama and Tombigbee rivers. Those dams are controlled by the U.S. Army Corps of Engineers and Alabama Power Co.

That idea was first proposed to officials and the Press-Register by Alabama Commissioner of Conservation and Natural Resources Barnett Lawley within days of the April 20 explosion of the Deepwater Horizon. Lawley said the idea was not well-received by the corps or Alabama Power. He said officials told him it would be too complicated.

Alabama Power spokesman Michael Sznajderman said the company's engineers looked into such a release after Lawley initially proposed it. He said there were a number of issues that would have to be considered, including the impact on people who live around the lakes behind the dams, whether communities along the river would still be able to draw drinking water, and whether the idea would even work.

"We simply don't know if it would have a benefit," Sznajderman said. "But we do believe you would have a number of potentially negative factors you'd have to consider."

A call late Tuesday to the corps was not immediately returned.

"Now maybe somebody will look at it," Lawley said. "It's just common sense. There's no question it is working so far, but it is all dependent on the amount of rain."

He speculated that each dam would have to allow a little more water to flow past it, in a carefully orchestrated effort.

"If we're handling all these floods up there, evidently we can handle moving extra water," Lawley said. "It would be a bullet you'd want to hold. They're thinking booms and skimmers will keep the oil out. That's a bunch of bull. Look at Louisiana. They had booms. They had skimmers.